1. Field of the Invention
The present invention generally relates to computer software. More specifically, the present invention relates to techniques for selective quantity takeoff from computer aided design drawings.
2. Description of the Related Art
The term computer aided design (CAD) generally refers to a broad variety of computer-based tools used by architects, engineers, and other construction and design professionals. CAD applications may be used to construct computer models representing virtually any real-world construct. Commonly, CAD applications are used to compose computer models and drawings related to design projects. For example, a CAD application may be used to compose a three-dimensional (3D) model of a house or an office building. Once composed, these CAD models are often used to generate a variety of two-dimensional (2D) and 3D views, such as plan, profile, section, and elevation views. Additionally, such models may be used to generate architectural, construction, engineering, and other documentation related to the design project.
A common requirement of design projects is to generate an estimate of the cost of the design project from the design drawings. This estimate can be used as part of the bidding process or as part of the pricing process. The term “quantity takeoff” refers to the process of generating estimates of quantities needed to construct the design project, based on the design drawings and specifications. The quantities may include numerical counts, such as the number of doors and windows in a project, but may also include other quantities such as a volume of material or a linear amount feet of material. Based on the quantity takeoff, generating the cost estimate for a design project typically involves selecting associated materials, determining labor costs, and generating the estimate of the cost of the project.
Typically, the quantity takeoff process is performed manually. For example, a project manager may use a printout, a pen, and a clicker to manually count objects illustrated in a set of construction documents. The project manager may physically mark each instance of an object in the construction documents, using the clicker to maintain an instance count. A digitizer may be used to take measurements of construction elements. However, performing quantity takeoff manually is laborious and error prone. Moreover, if the project design is modified after the original cost estimate is calculated, the takeoff process may need to be repeated. If the takeoff process is not repeated after design changes, accumulated inaccuracies in the cost estimate may adversely affect the bidding or pricing process.
To address these problems, some CAD applications have been configured to perform simplistic quantity takeoff computations from CAD drawings. These systems still have certain drawbacks, however. One specific drawback is that only one “object type” can be taken-off at a time. Object types define an abstract template of which specific instances a particular object are present in the CAD drawing. Taking off each object type separately can be a time consuming and laborious process if many different types of objects exist in the CAD model. These situations frequently arise in more complicated projects, such as those involving the design and construction of large office buildings, shopping malls, bridges, and tunnels, to name a few.
As the foregoing illustrates, what is needed in the art is a more effective and flexible technique for performing quantity takeoff computations in more complicated CAD models.